1. Field of Invention
This invention relates to an improved lighting device for use around swimming pools, walkways, signs and other decorative accent lighting.
2. Description of Prior Art
Illumination by means of radiation from the surface of an elongated substrate such as a rod or fiber finds wide application in area lighting, around swimming pools, walkways, signs, safety and decorative accent lighting. In such lighting systems, light energy is directed at one or both ends of the fiber whereupon portions of the light propagates through the core of the fiber and portions are scattered by controlled means laterally. The controlled conversion of the axial component of light energy travelling through the core of the fiber into lateral modes results in emission of light from the outer surface of the fiber
Optical fiber lighting apparatus available in the market today primarily employ two techniques for scattering the propagating light within the fiber into lateral modes for illumination. The surface of the core layer of such fibers are roughened to approximately 0.3 microns to scatter the light rays impinging the core/clad interface. Portions of the scattered light escape from the fiber and are radiated out of the fiber surface. A second technique uses radiation scattering centers dispersed within the core itself to scatter propagating light outwards so that they emerge from the outer surface of the fiber. The core dimensions are predominantly uniform throughout the entire length of the fiber. These arrangements do not permit efficient conversion of light energy incident at the end(s) of the fiber into laterally scattered energy for illumination purposes. Conventional illumination fibers therefore provide only low intensity lateral illumination.
The core of conventional illumination fibers are formed of extruded thermoplastics. Thermoplastics have low softening temperatures and therefore restrict the amount of radiant energy that can be incident at the end face(s). High light intensities result in high heat generation within the plastic core due to absorption and the heat build up may reach the critical softening temperatures of thermoplastics.
Conventional all-plastic fibers do not exhibit rigidity and therefore they require trays and channels for support. In certain applications rigidity and strength are important so that forming individual strands of the fiber into intricate shapes can be performed without the fiber damaging or abrading. Rigidity also enables the fiber to be self-supporting. Conventional illumination fibers do not have features that allow this capability.